Decorative surfaces for moldings, in particular made of a plastics material provided with a film, are very well known. United States patent application publication 2009/0001752 describes by way of example a process for the production of a thermoplastic film with a three-dimensionally structured, embossed surface. DE 10 2006 019 867 A1 in turn discloses a process for the production of thermoformable plastics moldings by the negative deep-draw process.
The decorative surface mostly comprises a coating, preferably an outer layer and/or lacquer layer, where the lacquer layer can be composed of one or more (up to six) identical or different formulations). These formulations are in each case composed of one or more polymer resins, one or more matting agents, and optionally various crosslinking components and other additives, for example for adjusting abrasion resistance, frictional behavior, haptic properties, rheology, and resistance to light and to heat. It is also conventional in industry to add colorant components, such as dyes and/or pigments.
The entire lacquer layer can be composed of a plurality of layers of identical or different formulations, and it is not necessary here that every layer comprises the above components. The decorative surface frequently has a two-layer lacquer system made of undercoat lacquer and topcoat lacquer, or else has a three-layer lacquer system made of primer, undercoat lacquer, and topcoat lacquer. The primer here is responsible for promoting adhesion between the substrate which forms the decorative surface and the lacquer layers above them. The undercoat lacquer can have a plurality of functions: by way of example the provision of mattness, promoting adhesion between substrate and topcoat lacquer, etc. The topcoat lacquer generally has the function of adjusting the properties of the decorative surface to customer requirements.
Formulations of this type are disclosed by way of example in U.S. Pat. Nos. 8,314,179, 6,682,779, or else in DE 10 2009 049 630 A1. U.S. Pat. No. 8,314,179 describes water-based polymer mixtures for decorative surfaces for improvement of long-term functionality, while DE 10 2009 049 630 A1 discloses water-based and NMP-free polymer mixtures and application thereof to films for decorative surfaces. U.S. Pat. No. 6,682,779 describes water-based polyurethane lacquers for elastomers which comprise at least one compound having blocked isocyanate groups.
For the production of three-dimensional decorative surfaces from a flat plastics material, preferably a deep-draw film, the plastics material has to be subjected to stretching. Partial stretching factors up to 500% or more can arise, depending on the geometry of the component. A coating, preferably a lacquer system, is provided to deep-draw films of this type while they are still flat, and the films are then mostly embossed with a decorative grain. The lacquers used in this production variant are also termed deep-draw lacquers. Alternatively, lacquered deep-draw films are subjected to stretching and are embossed in the component.
The decorative grain on the decorative surface is composed of elevations, which are termed grain peaks, and depressions, which are termed grain valleys. During the embossing of the decorative grain the deep-draw lacquer is subjected to different degrees of stretching. In the region of the grain valleys the deep-draw lacquer is subjected to a greater degree of stretching than in the region of the grain peaks.
When this embossed film is then processed to give the component, for example by means of deep drawing, the entire decorative surface is also subjected to stretching. There are likewise different degrees of stretching here. The deep-draw lacquer is subjected to a greater degree of stretching in the region of the grain valleys than in the regions of the grain peaks. If the tensile strain at break of the deep-draw lacquer is exceeded, break-up of the decorative surface occurs. This break-up is discernible inter alia as graying and/or glossy spots in the grain valleys. Surface defects of this type are undesirable.
A summary of the disadvantages of the films disclosed hitherto in the decorative surface is as follows:                The decorative surface is intended to have uniform mattness depth. This mattness in the flat product cannot be retained on the entire final decorative surface during component production.        The decorative surface exhibits a stretching-dependent nonuniform increase of gloss level. The desired uniform mattness over the entire decorative surface is therefore not obtained.        In highly stretched regions the decorative surface exhibits areas of increased gloss, in particular in grain valleys, caused by microcracks or the like. Graying of the decorative surface also frequently occurs.        The emissions from decorative surfaces for moldings made of a plastics material provided with a film in the interior of an automobile do not meet the requirements of the market, firstly in quantitative terms, that is, excessive emissions, and secondly in qualitative terms, by way of example because of the presence of toluene.        The cleavage temperature required for the reaction with blocked isocyanate groups requires temperature-dryer-residence-time profiles which are not achievable, in either technical or operating-cost terms, for decorative-surface films. The blocking agent used for the blocked isocyanate groups also generates undesirable emissions and odors.        
The decorative surfaces disclosed in the publications mentioned, which are merely examples, therefore no longer meet current market requirements.